In liquid-crystal projectors using a transmission type liquid-crystal panel as a light modulating element, there exists a liquid-crystal projector in which a micro-lens (hereinafter also described as “ML”) is provided on the surface of a liquid-crystal panel corresponding to each pixel in order to increase a quantity of light incident on an effective area of pixel.
FIG. 1 is a diagram showing an example of a conventional arrangement of a main portion of a lighting optical unit in a liquid-crystal projector using a liquid-crystal panel with ML compared with a lighting optical unit of a liquid-crystal projector using a liquid-crystal panel without ML.
In the lighting optical unit of the liquid-crystal projector using the liquid-crystal panel without ML, as shown in FIG. 1A, light emitted from a light-source lamp 11 is reflected by a parabola-like reflector 12 to be collimated into a bundle of rays, and thereafter the light is made to be uniform by first and second fly-eye lenses 13, 14 (integrators for superimposing light at the central portion and light at the peripheral portion of the light-source lamp 11 so that light is uniformly irradiated on the liquid-crystal panel), converged by a main condenser lens 15 and channel condenser lens 16 and then irradiated on a liquid-crystal panel 17 without ML.
The optical system from the fly-eye lens 13 to the condenser lens 16 is designed and manufactured in such a manner that the system has a numerical aperture through which a quantity of light incident on the effective area of the pixel of the liquid-crystal panel 17 becomes approximately maximum and that the system has an entrance pupil diameter approximately equal to the diameter of a beam spot of a bundle of parallel rays from the reflector 12.
On the other hand, in the liquid-crystal projector using the liquid-crystal panel with ML, as shown in FIG. 1B, light from the same light-source lamp 11 as that in FIG. 1A is reflected by the same reflector 12 as that in FIG. 1A to be collimated into a bundle of parallel rays, and thereafter the light is made to be uniform by first and second fly-eye lenses 18 and 19, converged by a main condenser lens 20 and channel condenser lens 21 and then irradiated on a liquid-crystal panel with ML 22 (ML is provided on the surface of the liquid-crystal panel having the same structure as that of the liquid-crystal panel 17 shown in FIG. 1A).
The optical system from the fly-eye lens 18 to the channel condenser lens 21 is designed and manufactured such that the system may have a numerical aperture smaller than that of the optical system from the fly-eye lens 13 to the channel condenser lens 16 shown in FIG. 1A.
The reason for that will be described below. In the liquid-crystal projector having the lighting optical unit shown in FIG. 1A, when the liquid-crystal panel 17 is replaced with the liquid-crystal panel with ML 22, light refracted by the ML may be introduced into other portions than the effective area of the pixel of the liquid-crystal panel with ML 22. Therefore, there is a possibility that a quantity of light incident on the effective area will decrease. In order to prevent light refracted at the ML from entering into other portions than the effective area, a maximum conical angle of light incident on the liquid-crystal panel with ML 22 should be reduced. Thus, the optical system from the fly-eye lens to the channel condenser lens is designed and manufactured to have a small numerical aperture, thereby decreasing the maximum conical angle.
As described above, in the conventional liquid-crystal projector using the liquid-crystal panel with ML, as the optical system in the lighting optical unit for irradiating light from the light-source lamp on the liquid-crystal panel in a uniform and/or convergent manner (optical system from the fly-eye lens 18 to the channel condenser lens 21 in FIG. 1B), there has hitherto been designed and manufactured the optical system having the numerical aperture smaller than that of the liquid-crystal projector using the liquid-crystal panel without ML.
However, there are disadvantages in the prior-art technique as the following (a) to (c):
(a) In the liquid-crystal projector using the liquid-crystal panel with ML, when a numerical aperture of the optical system in the lighting optical unit for irradiating light from the light-source lamp on the liquid-crystal panel in a uniform and/or convergent manner is reduced, the F number of this optical system becomes large. Specifically, assuming that the F number of the optical system in the lighting optical unit of the liquid-crystal projector using the liquid-crystal panel without ML falls within a range of approximately 2.2 to 2.5, then the F number of the optical system in the lighting optical unit of the liquid-crystal projector using the liquid-crystal panel with ML becomes 3 or larger.
Consequently, in the liquid-crystal projector using the liquid-crystal panel with ML, as shown in FIG. 1B, since the optical path length of the lighting optical unit increases, the outside dimension of the lighting optical unit increases, and as a result the whole of the liquid-crystal projector may become large in size.
(b) When the liquid-crystal projector using the liquid-crystal panel with ML and the liquid-crystal projector using the liquid-crystal panel without Ml are both manufactured, as the optical systems in the lighting optical units, there should be designed and manufactured optical systems having different numerical apertures for both the optical system, respectively. Accordingly, even though the optical assemblies comprising the two optical systems have the same function (e.g. the fly-eye lens 13 in FIG. 1A and the fly-eye lens 18 in FIG. 1B), their specifications become different from each other.
Accordingly, since the optical assemblies cannot be made common to those optical systems, it is difficult to reduce costs of assemblies.
(c) When the liquid-crystal projector using the liquid-crystal panel with ML and the liquid-crystal projector using the liquid-crystal panel without ML are both manufactured, the arrangement operations for the optical systems in the lighting optical units should be carried out separately. Therefore, it is difficult to make a manufacturing operation more efficient.
In view of the aforesaid aspects, it is an object of the present invention to remove the disadvantages with respect to the conventional lighting optical unit of the liquid-crystal projector using the liquid-crystal panel with ML.